Electrical component

ABSTRACT

An electrical component, e.g., a press-in diode, is provided, which is suited for high currents and which ensures reverse-polarity protection. The electrical component includes at least one chip which is connected via soldering layers to a lead wire and a base. In the event of a rising temperature caused by polarity reversal, the clamp-type connection between the individual parts of the electrical component, e.g., the lead wire and the base, is released since the connecting plastic sheath softens, resulting in the release of the clamp-type connection, thereby interrupting the electrical connection and thus a current flow. At normal operating temperature, the clamp-type connection between the individual parts of the diode is ensured via a plastic sheath and a plastic sleeve, with bulges of the lead wire and the base protruding into the plastic sheath, thereby making the connection particularly stable.

FIELD OF THE INVENTION

The present invention relates to a press-in diode sheathed with plastic.

BACKGROUND INFORMATION

The basic construction features of press-in diodes which are sheathedwith plastic are described in published German patent documents DE 43 41269 and DE 195 49 202. An example of this type of diode is illustratedin FIGS. 3 and 4. Such press-in diodes are used in the rectifier bridgeof alternators in motor vehicles, for example. Suitable reverse-polarityprotection is necessary to prevent damage in the event of an incorrectconnection of the vehicle battery. A reverse-polarity protectionelement, suitable for use in alternators in motor vehicles, is describedin published German patent document DE 100 05 183.

SUMMARY OF THE INVENTION

The present invention provides an electrical component, e.g., a press-indiode sheathed with plastic, which operates securely and reliably in awide temperature range, i.e., which may be used in such a widetemperature range. A secure clamp-type connection between the lead wireand the base is ensured in the usual operating temperature range of thediode (approximately 230° C.), and in the event of an over-temperature(approximately 400° C.), which may occur, for example, when the batteryis connected with false polarity, the clamp-type connection disengagesand causes an interruption in current flow, thereby avoiding furtherheating and at worst inflammation of the plastic.

These advantages are achieved by providing a diode, particularly apress-in diode, in which a chip, forming the p-n junction, is connectedvia soldering layers to two parts, particularly a lead wire and a base.The press-in diode is designed in such a way that, at least in the chiparea, a plastic sheath and a sleeve form a connection which acts as aclamp-type connection, at least one part having a predefinable bulgewhich protrudes into the plastic sheath, thereby forming a fixedconnection in the normal state. In the event of overheating, whichoccurs in the event of polarity reversal for example, i.e., connectionof the electrical component to a voltage source with false polarity, theplastic softens and the clamp-type connection disengages, therebyinterrupting the current flow through the electrical component, thediode, for example. The disengagement of the clamp-type connection isfurther increased if forces act which cause the two parts to be pulledor pushed apart when the plastic is softened. Such forces are created inan advantageous manner by the temperature-dependent expansion of theplastic.

It is advantageous that simple mechanically constructive features resultin secure fixing and simultaneous reverse-polarity protection. This isparticularly true for the advantageous use of the electrical component,a diode for example, in a rectifier system in a motor vehicle. If ashort circuit occurs, e.g., as a result of an incorrect batteryconnection, the current flow through the diodes of the rectifier isinterrupted and excessive overheating of vulnerable components isprevented so that flammable parts of the alternator or the supply linescannot ignite. The selection of a suitable plastic or another material,which softens at desired temperatures, makes it possible to adjust thedisengagement of the clamp-type connection within a certain temperaturerange.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a shows a conventional press-in diode.

FIG. 1 b shows an exemplary embodiment of a press-in diode according tothe present invention.

FIG. 1 c shows another exemplary embodiment of a press-in diodeaccording to the present invention.

FIG. 1 d shows a further exemplary embodiment of a press-in diodeaccording to the present invention.

FIG. 2 illustrates an exemplary method of manufacturing a portion of apress-in diode according to the present invention.

FIG. 3 illustrates a conventional method of manufacturing a portion of apress-in diode.

FIG. 4 illustrates a conventional method of manufacturing a portion of apress-in diode.

DETAILED DESCRIPTION

FIG. 1 b shows the electrical component (diode) according to the presentinvention, and FIG. 1 a shows the component (diode) having a housingtype described in published German patent document DE 195 49 202.

The diode (in both FIGS. 1 a and 1 b) is composed of a base 1, alsoreferred to as first part, and a lead wire 2, also referred to as secondpart, the lead wire having a partly conical design in the known diode(FIG. 1 a) and a partly cylindrical design in the approach according tothe present invention (FIG. 1 b). A chip 3, which forms the actual p-njunction, is mechanically and electrically connected to base 1 and leadwire 2 via two soldering layers 4. A protective sleeve 5 encloses atleast the junction area between base 1 and lead wire 2 in which chip 3is also situated, thus forming a type of housing together with base 1.The space between protective sleeve 5 and the remaining parts is filledwith plastic 6.

In the diode shown in FIG. 1 b, base 1 has an undercut 8 and the leadwire has an undercut 8 a, which both protrude into plastic 6 causing afixed connection when the plastic is firm. Base 1 and lead wire 2 arethus clamped together. The exemplary diode according to the presentinvention shown in FIG. 1 b differs from the diode of FIG. 1 a (e.g.,described in published German patent document DE 195 49 202) in thearrangement and manufacture of undercut 8 on diode base 1 (as well as byarrangement and manufacture of undercut 8 a on lead wire 2). Theelectrical component according to FIG. 1 b is a fixed unit at usualtemperatures, which component is stable even in the presence of forceswhich generally act between base 1 and lead wire 2 and would pull thetwo parts apart. In the known diode according to FIG. 1 a, base 1 hasonly one bulge 10 protruding into plastic 6.

In addition to base 1, lead wire 2 may also be designed in such a waythat it has its own undercut 8 a, which protrudes into plastic 6, asshown in FIG. 1 b.

When the electrical component is connected with a false polarity, a highcurrent, causing excessive heating, flows between the two parts via thethen conductive chip. Since the plastic also heats up at highertemperatures which occur in the event of a polarity reversal, theplastic also softens and expands with the rising temperature. Due to theexpansion of the plastic in the area between the lead wire and the base,forces are created which push the lead wire and the base apart. However,since the plastic simultaneously softens at the high temperature of upto 400° C. prevailing during the polarity reversal, the fixed clamp-typeconnection between the parts disengages and the current flow between thetwo parts through the chip, which is conductive due to the polarityreversal, is interrupted, thereby achieving the desired reverse-polarityprotection.

Two further embodiments according to the present invention areillustrated in FIGS. 1 c and 1 d, which represent the combinations ofthe approaches illustrated in FIGS. 1 a and 1 b. Although theembodiments of the diodes according to the present invention arerotationally symmetric, approaches which are not rotationally symmetricare also conceivable. It is essential that at least one part, either thebase or the lead wire, has at least one predefinable bulge or undercutwhich protrudes into the plastic and forms a fixed connection when theplastic is firm, but which connection disengages when the plastic issoft, particularly liquid, i.e., at high temperatures.

The electrical component according to the present invention, a diode forexample, differs from the diodes described in published German patentdocuments DE 43 41 269 and DE 195 49 202 due to the type and manufactureof undercut 8 on diode base 1 and/or undercut 8 a on lead wire 2.Detailed information about the manufacture of diodes is given in FIGS.2, 3, and 4.

FIG. 2 shows how an undercut 8 on base 1 of the diode according to thepresent invention may be created using a punching tool 7 or, if needed,by further processing. Undercut 8 may be designed as a circumferentialcollar. Punching tool 7 exerts a pressure on, for example, rotationallysymmetric area 13 and deforms it. This deformation does not reduce thesurface of the base facing the chip after assembly. The undercut isplaned in an additional second work step. This creates undercut 8 on thediode base illustrated in FIG. 1 b which, together with the adjacentsurface of the base, forms an optimally large supporting surface ontowhich the chip may be deposited.

In contrast to this, in the manufacturing method known from publishedGerman patent document DE 195 49 202 and outlined in FIG. 3, part ofbase 1 is peeled and formed into bulge 10 using a cylindrical peelingtool 9, the bulge forming a circumferential collar. The surface of base1 is reduced here, while in the approach according to the presentinvention shown in FIG. 2, the surface of base 1 and thus thechip-supporting surface is not reduced.

FIG. 4 shows another possibility for creating a collar for the base of apress-in diode which is known from published German patent document DE43 41 269. A rotationally symmetric extension 12 of base 1 is used herefor creating the collar of the base, the extension being given a desiredform using a form tool 11.

Identical measure b creates a maximum diameter A of the chip-supportingsurface, as shown in FIGS. 1 a and 1 b. The housing according to thepresent invention formed by base 1, sleeve 5, plastic 6, and lead wire 2may accommodate a larger silicon chip than the known housing and istherefore suited for higher currents. In an embodiment in which diameterB equals 10.3 mm, B being the inside diameter of the plastic sleeve, thechip-supporting surface on a base according to published German patentdocument DE 195 49 202 may have a maximum diameter A of 8 mm; in theembodiment according to the present invention, however, it may have amaximum of 9.2 mm.

The same is true for the comparison with the embodiment according topublished German patent document DE 43 41 269. In this known approach,the wall thickness of the collar always takes up part of thechip-supporting surface, so that this surface will always be smallerthan is the case in the approach according to the present invention.

Using the height and the wall thickness of the collar, measure a ofundercut 8 (e.g., shown in FIG. 1 b) may be adjusted in the approachaccording to the present invention. Measure a should be selected in sucha way that, at the diode's normal operating temperature of, for example,a maximum of 230° C., plastic 6 sufficiently clamps lead wire 2 and base1. In the event of inadvertent polarity reversal of the battery in themotor vehicle, when the positive pole of the battery is connected to thediode's anode and the negative pole is connected to the cathode, thediode should interrupt the current flow before the plastic insulation ofthe alternator or the battery cable ignites due to overheating. Thisrequirement may be met if the clamp-type connection in the diode isreleased at a maximum of 400° C. as a result of the softening of usedplastic 6 and subsequent disengagement of the base 1 and lead wire 2.

The thermal expansion of the diode's plastic in a concrete exampleequals 30 ppm/K. Together with the thermal expansion of copper, thediode base material, a calculation results in a maximum undercut a ofapproximately 0.05 mm. Such small undercuts are not producible using themethods as described in the published German patent documents DE 43 41269 or DE 195 49 202. Typical values in the known approaches lie around0.2 mm.

The design of the lead wire according to FIG. 1 b supports the openingof the diode during polarity reversal of the battery if, also in thiscase, undercut a does not exceed 0.05 mm. As an additional advantage ofthis lead wire, it should be pointed out that measure l is minimized incomparison with the known approaches. As explained in published Germanpatent document DE 43 41 269, the diode's plastic sheathing may absorban increasing tensile load as l decreases. Typical values of l for theknown housings lie around l=1 mm; however, for the approach according tothe present invention, the typical values of l lie around l=0.5 mm.

In summary, the present invention provides a press-in diode for highcurrents including built-in polarity reversal protection since theclamp-type connection is automatically released in the event ofoverheating caused by polarity reversal.

1-11. (canceled)
 12. A press-in diode, comprising: a base; a chipoperatively connected to the base by a first soldering layer; a leadwire operatively connected to the chip by a second soldering layer; aplastic sheathing laterally surrounding at least the chip and regions ofthe base and the lead wire adjacent to the chip; and a protective sleevelaterally enclosing the plastic sheathing; wherein the chip and the leadwire each have a predefined bulge that laterally protrudes into theplastic sheathing, whereby a clamp-type connection between the base andthe lead wire is formed by the interaction of the bulges with theplastic sheathing enclosed by the protective sleeve.
 13. The press-indiode according to claim 12, wherein the bulges are rotationallysymmetric.
 14. The press-in diode according to claim 12, wherein thediode is an integral part of a rectifier system.
 15. The press-in diodeaccording to claim 12, wherein the plastic sheathing is made of aplastic that is firm in a first temperature range and is soft in asecond, higher temperature range.
 16. The press-in diode according toclaim 13, wherein the plastic sheathing is made of a plastic that isfirm in a first temperature range and is soft in a second, highertemperature range.
 17. The press-in diode according to claim 15, whereinthe first temperature range has a maximum of 400° C.
 18. The press-indiode according to claim 15, wherein the clamp-type connection betweenthe based and the lead wire is ensured when the plastic is firm, andwherein a release of the clamp-type connection occurs when the plasticis soft.
 19. The press-in diode according to claim 18, wherein anelectrical connection among the base, the chip and the lead wire isinterrupted when the clamp-type connection is released.
 20. A method forproducing a base component of a press-in diode having a chip interposedbetween the base and a lead wire, the method comprising: providing alateral bulge on the base component by initially deforming a verticalelement extending from the base component by applying a pressure and bysubsequently performing a planarization.
 21. The method according toclaim 20, wherein the pressure is generated using a punching tool. 22.The method according to claim 20, wherein the vertical element forforming the lateral bulge is a circumferential collar that isrotationally symmetric.